The specific aim of the proposed set of studies is to prospectively examine immediate and long-term (up to 2 years) adjustment outcomes (i.e., posttraumatic stress disorder symptoms, depression symptoms, and anxiety symptoms) following the mass shooting that occurred on the Northern Illinois University (NIU) campus in DeKalb, Illinois, on February 14, 2008. At the time of the shooting, a large sample (N = 816) of female undergraduates at NIU were participating in a longitudinal study of sexual revictimization. Given the trauma- focused nature of the revictimization study, it provided a unique opportunity to examine post-shooting adjustment outcomes while controlling for pre-shooting adjustment levels. To date, 653 women (80% of eligibles) have completed an online survey, NIU Trauma Study (NTS): Time 1, an average of 27 days after the mass shooting. The survey contained assessments of post-shooting adjustment, degree of exposure to the shooting, and additional risk and protective factors (e.g., social support, posttraumatic growth). Additional assessments are proposed for 3.5 months, 7.5 months, 1 year, and 2 years post-shooting. Several factors are hypothesized to influence changes in adjustment in the aftermath of the trauma. These include pre-shooting risk factors [e.g., childhood or other trauma exposure, dysregulation of stress hormones (i.e., pre-shooting salivary cortisol levels), and dysfunctional affect regulation strategies], factors associated with the shooting (e.g., severity of exposure), and immediate reactions to the mass shooting (e.g., peritraumatic dissociation and affect regulation strategies for coping with shooting-related distress). In addition to direct effects of proposed risk and protective factors on changes in adjustment level across the six time points, a number of interactive effects will also be tested. Following the 1-year post-shooting assessment, a subset of participants (N = 160) will be recruited to participate in a clinical reappraisal study in order to calibrate the self-report screening measures to gold-standard face-to-face structured diagnostic interviews. In addition, a unique laboratory-based study [Expressive Writing Study (EWS)] is also proposed for a subset of participants (N = 100) who at NTS: Time 1 report high and low exposure to the shooting. In the EWS, participants will write about the mass shooting and then read their essay aloud to themselves while their physiological data are collected. One aim of the EWS is to examine whether physiological reactivity, salivary cortisol changes, and self-reports of emotional avoidance during the EWS are predictive of longer-term outcomes in adjustment as a function of severity of exposure to the shooting. The specific content of the expressive writing will also be examined. Longitudinal follow-up data on adjustment from the NTS survey will also serve as follow-up data for the EWS. In combination, data from these proposed projects will provide crucial and unique information about the role of risk factors and protective factors in predicting adjustment following a mass shooting. If successful, the proposed research will (i) provide information regarding the psychological consequences of experiencing or witnessing a mass shooting while controlling for pre-shooting levels of symptoms and adjustment;(ii) identify the direct and moderating effects of pre-shooting adjustment (e.g., trauma history, dysfunctional affect regulation, dysregulation of stress hormones) on post-shooting adjustment outcomes;and (iii) provide information regarding the physiological reactivity (and recovery) of engaging in an expressive writing and reading task as a function of exposure to the mass shooting. The proposed set of studies seeks to promote NIH's interests in understanding, from a longitudinal perspective, the factors (risk and protective) that contribute to the development of posttraumatic stress disorder and other trauma-related mental illnesses.